The invention is especially useful for conditioning aqueous medium in aquariums wherein aquatic life such as fish, lobsters, shrimp and other marine life are grown and maintained for domestic or commercial purposes.
It should be understood that aquariums as used herein is not limited to the small, about 1-10 cubic feet, sized containers often seen in homes for decoration or hobby purposes, but they also include the much larger containers used for marine life habitats often referred to as tanks, including commercial above- or below-ground tanks containing hundreds, thousands, and millions of cubic feet of water.
It should also be understood that the method and apparatus of this invention are useful in removing ammonia or nitrite from certain industrial wastewater streams.
Marine aquarists have long recognized the problem of buildup of nitrogen compounds. In the aquarium, toxic nitrogen compounds, especially ammonia, are the products of decomposition of various organic materials among which are uneaten food; slime, excrement, and urine from marine life; and various microorganisms. Some of these materials may be excreted directly by organisms also. Even well-managed aquaria usually contain three to six times the normal amount of nitrogen compounds found, for example, in natural sea water. Older established aquaria may contain ten times or more the normal amount of these compounds. This is an unnatural condition imposed upon marine organisms, for in their native habitats natural nitrogen cycling processes keep dissolved nitrogen compounds down to very low levels. Over long periods of time, excessive buildup of toxic nitrogen compounds in artificial environments affects marine fishes adversely such as by reducing their resistance to diseases, thereby decreasing their life spans or by killing them directly. Normally, ordinary marine filter materials such as charcoal, chalk, etc., do not significantly detoxify or remove these common nitrogen compounds.
Many other filtering solutions have been sought which would maintain the water of an aquarium as close as possible to that of the natural water. The marine life sought to be maintained in the aquariums is adapted to and does best in water like that of its natural habitat. These filtering methods have included passing the aquarium water through open-cell polymeric foam. See, for example, the following patents: U.S. Pat. No. 3,957,017; U.S. Pat. No. 3,347,211; U.S. Pat. No. 3,578,169; U.S. Pat. No. 3,891,555; G.B. Pat. No. 1,262,625; U.S. Pat. No. 4,076,619; U.S. Pat. No.3,301,402; U.S. Pat. No. 2,539,768; and U.S. Pat. No. 4,076,619. It will be seen from a study of these patents that although they teach the use of such polymeric foam material and the like as a filtering agent for aquariums, they nevertheless all teach their use when the foams etc. are submerged.